The invention relates to an air spring.
A known air spring for use between relatively-vibrating bodies has a variable interior space filled with air at a mean pressure for spring action between the bodies, connected to a compressed-gas reservoir through a supply line having an intake valve, and provided with an outlet valve. A control device detects the pressure in the variable interior space, opens the outlet valve when the pressure rises above the mean pressure, and opens the intake valve when the pressure drops below the mean pressure to compensate for vibration-produced pressure variations in the interior space.
For example, German patent publication DAS No. 12 82 475 discloses a pneumatically-damped air-suspension system in which a double-acting valve connects the variable interior space of an air spring to an equalizing space. The valve is actuated by vibration-induced pressure differentials between the interior space of the air spring and the equalizing space to provide some compensation for the over- or under-pressures in the air spring producing the pressure differentials. However, the damping action so obtained is not fully satisfactory because the pressure compensation in the air spring to counteract vibration-induced pressure differentials is actually confined within very narrow limits by essentially-identical mean pressures in the equalizing space and the interior space of the air spring. This basic situation remains the same even if the valve is connected to a separate damper. The isolating action therefore falls short of satisfying stringent requirements, except in rare cases.